As networks continue to grow, physical adjacency detection becomes more complex. As described herein, physical adjacency detection refers to determining which ports on which network elements, switches, nodes, etc. are connected to one another, i.e., adjacency is interconnection. Various conventional techniques for adjacency detection exist. In Time Division Multiplexing (TDM) protocols such as Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH), and Optical Transport Network (OTN) can have overhead such as the Trail Trace Indicator (TTI) field which detects adjacency. In Layer 2, the Link Layer Discovery Protocol (LLDP) is used by network devices for advertising their identity, capabilities, and neighbors on an IEEE 802 local area network, principally wired Ethernet. Additionally, various proprietary vendor solutions exist as well. For example, Ciena Corporation has implemented Service and Photonic Layer Interoperability (SPLI) on line side optics for adjacency detection and other functionality. Other approaches include using dither to modulate waveform depth on optics, using acoustic signals in addition to optical signals, and the like. All of these aforementioned techniques have similar limitations. Specifically, each of the above is either dedicated to a single layer (Layer 1 as in TTI, Layer 2 as in LLDP, etc.) or is proprietary to a single vendor (e.g., dither, acoustic, etc.). Another solution is to turn connections (lasers) on and off to detect adjacency. Of course, this approach affects traffic and is not in-service. Since practical network deployments are multi-layer and multi-vendor, there exists a need for physical adjacency detection systems and methods to operate in such deployments.